For example, a 2018 study revealed that following 12 weeks of probiotic treatment (8 ​× ​109 ​CFU/day), gene expression of IL-1, IL-8, and TNF were downregulated in PBMCs from individuals with PD compared to those in the placebo group [139], indicating a potential beneficial anti-inflammatory effect of probiotics on peripheral blood immune cells. Here, TNF is linked to Parkinson disease.